Core wire for a guide wire comprising a functionally graded alloy

ABSTRACT

Guide wires and catheters made from a functionally graded alloy comprising 3-10 weight % Al and 5-20 weight % Mn, the balance being substantially Cu and inevitable impurities. The functionally graded alloy is produced by forming the copper-based alloy, maintaining it at a temperature of at least 500° C. and rapidly cooling it, and then subjecting the alloy to an aging treatment by a gradient temperature heater.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application is a divisional of Ser. No. 09/339,929,filed Jun. 25, 1999, the entire contents of which are herebyincorporated by reference.

FIELD OF THE INVENTION

[0002] The present invention relates to a core wire for a guide wirebased on a copper-based, functionally graded ally having uniformcomposition and diameter and continuously or stepwise changingproperties such as hardness, modulus elongation, etc. These guide wirescan be used in catheters and the like.

BACKGROUND OF THE INVENTION

[0003] Functionally graded alloys are materials having continuously orstepwise changing properties such as hardness, elasticity, thermalconductivity, electrical conductivity, etc., without developing agradient in size with mechanical working such as cutting or the like, orchemical treatment such as etching or the like. Functionally gradedmaterials developed to date are mostly two-component composites such asSiC/C, ZrO/W, TiC/Ni, ZrO/Ni, etc. These materials have graduallychanging mixing ratios.

[0004] Conventional functionally graded materials having graduallychanging mixing ratios have been produced by mixing different materialpowders at gradually changing mixing ratios to prepare a plurality ofmixed powder sheets having gradually changing mixing ratios, laminatingthe mixed powder sheets along the gradually changing mixing ratios,compacting them, and sintering them. For example, Japanese Laid-OpenPatent No. 5-278158 discloses a functionally graded, binary metalmaterial produced by laminating and sintering tungsten powder andmolybdenum powder at a gradually changing mixing ratio.

[0005] However, functionally graded materials produced by this methodcannot be rolled or drawn, and they can be formed into desired shapesonly by cutting. Thus, they are not only very expensive, but they alsocannot be formed into complicated shapes. Accordingly, conventionalfunctionally graded materials are used mainly in highly expensiveapplications, such as spacecraft, nuclear power generators, etc. Thus,it is very desirable to develop less expensive and easily formablefunctionally graded materials.

[0006] Alloys having shape recovery properties and superelasticity arewidely used in various applications such as guide wires, catheters, etc.To introduce a catheter into a blood vessel and place it at a desiredsite in the blood vessel, a guide wire for guiding the catheter is firstintroduced into the desired site in the blood vessel, and the catheteris guided to the desired site in the blood vessel along the guide wire.Because human blood vessels wind and branch differently depending uponthe individual, guide wires having high introduction operability andtorque conveyance are required to insert the guide wires withoutdamaging the blood vessel walls.

[0007] For this purpose, a guide wire is composed of a core wirecomprising a tip end potion which is made soft by reducing its diameter,and a body portion which is relatively rigid. A coating layer is formedon the core wire, the coating being made of a synthetic resin which isinert with respect to the human body, such as polyamides, thermoplasticpolyurethanes, fluoroplastics, etc.

[0008] The guide wire usually comprises a coil-shaped metal wire made ofa material such as carbon steel or stainless steel. However, since wiresmade of these materials are easily bent, superelastic metals such asNi—Ti alloys and the like are used for the core wires of guide wires(Japanese Patent Publication No. 2-24549). However, superelastic Ni—Tialloys lack rigidity, even though they are sufficiently soft for thisuse. Therefore, they are not useful for insertion into a blood vessel,sometimes making it difficult to place them at a desired location in theblood vessel.

[0009] Additionally, because Ni—Ti alloys are relatively poor withrespect to cold working, they are not easily formed into thin wiressuitable for use as guide wires and the like. With respect to thegradient properties from heat treatment, it is difficult to provide theguide wire with the gradient needed to control the torque conveyance ofthe guide wire.

[0010] The same is true of catheters made of Ni—Ti alloys. The Ni—Tialloy catheters are not easily inserted into a blood vessel. Also, Ni—Tialloys cannot be easily formed into thin wires or pipes. Furthermore,the Ni—Ti alloys are poor in weldability and adhesion, posing problemswhen combined with other materials.

SUMMARY OF THE INVENTION

[0011] It is an object of the present invention to provide aninexpensive functionally graded alloy having excellent workability and amethod for producing such a functionally graded alloy.

[0012] It is another object of the present invention to provide a corewire for a guide wire comprising a soft tip end portion and a properlyelastic and rigid body portion which is readily insertable and hasexcellent torque conveyance and workability, as well as a guide wirecomprising such a core wire.

[0013] It is a further object of the present invention to provide acatheter comprising a soft tip end portion and a properly elastic andrigid body portion which is readily insertable, and has excellent torqueconveyance and workability.

[0014] As a result of research on previously proposed shape memory alloyCr—Al—Mn having a β-phase structure (Japanese Laid-Open Patent No.7-62472), the inventors have found that when the shape memory Cu—Al—Mnalloy having a β-phase structure is partially heated at particulartemperatures or at gradually changing temperatures, the shape memoryCu—Mn—Al is provided with a partially different crystal structure, whichexhibits remarkably gradient properties. The present inventors have alsofound that by giving gradually changing properties to the Cu—Al—Mn alloyby heat treating the alloy at a proper temperature gradient, guide wiresand catheters can be produced from this Cu—Al—Mn alloy which haveimproved insertion capabilities and torque conveyance. The presentinvention has been completed based upon these findings.

[0015] The functionally graded alloy of the present invention has acomposition comprising 3-10 weight % Al, 5-20 weight % of Mn, with thebalance Cu and inevitable impurities. The alloy comprises a firstportion composed essentially of a β-phase, a second portion composedessentially of an α-phase and a Heusler phase, and a third portionhaving a crystal structure continuously or stepwise changing from thefirst portion to the second portion.

[0016] The method for producing the functionally graded alloy accordingto the present invention comprises the steps of:

[0017] a. forming a copper-based alloy having a composition comprising3-10 weight % Al, 5-20 weight % of Mn, the balance being substantiallyCu and inevitable impurities, into a desired shape;

[0018] b. maintaining the copper-based alloy at a temperature of 500° C.or more and rapidly cooling the alloy to transform the crystal structurethereof substantially to a β-phase; and

[0019] c. subjecting the copper-based alloy to an aging treatment in aheater having a temperature gradient, thereby heating the first portionto less than 250° C., the second portion to 250-350° C., and the thirdportion to a temperature continuously or stepwise changing from theheating temperature of the first portion to the heating temperature ofthe second portion.

[0020] A core wire for a guide wire according to the present inventioncomprises a body portion having high rigidity and a tip end portionhaving a lower rigidity than that of the body portion, at least part ofthe core wire being made of a copper-based alloy comprising 3-10 weight% of Al, 5-20 weight % of Mn, with the balance being substantially Cuand inevitable impurities.

[0021] The guide wire according to the present invention comprises acore wire comprising a body portion having high rigidity and a tip endportion having a lower rigidity than that of the body portion, at leastpart of the core wire being made of a copper-based alloy comprising 3-10weight % of Al, 5-20 weight % of Mn, with the balance beingsubstantially Cu and inevitable impurities.

[0022] A catheter according to one embodiment of the present inventionis at least partially constituted by a metal pipe, the metal pipe havingat least a tip end portion made of a copper-based alloy comprsiing 3-10weight % of Al, 5-20 weight % of Mn, with the balance beingsubstantially Cu and inevitable impurities.

[0023] A catheter according to another embodiment of the presentinvention contains a reinforcing metal member in at least part of thecatheter tube, the reinforcing metal member being made of a copper-basedalloy comprising 3-10 weight % of Al, 5-20 weight % of Mn, with thebalance being substantially Cu and inevitable impurities.

BRIEF DESCRIPTION OF THE DRAWINGS

[0024]FIG. 1 is a schematic view showing an example of a gradienttemperature heater.

[0025]FIG. 2 is a graph showing the hardness distribution and the agingtemperature distribution of the functionally graded alloy wire of SampleNo. 3 in Example 1.

[0026]FIG. 3 is an optical photomicrograph showing the microstructure ofthe low-aging temperature portion of the functionally graded alloy ofSample No. 1 in Example 1.

[0027]FIG. 4 is an optical photomicrograph showing the microstructure ofthe high-aging temperature portion of the functionally graded alloy ofSample No. 1 in Example 1.

[0028]FIG. 5 is a graph showing the relation between the agingtemperature and the hardness of Samples Nos. 2 and 3 in Example 2.

[0029]FIG. 6 is a graph showing the relation between the aging time andthe hardness of Samples Nos. 5 and 6 in Example 3.

[0030]FIG. 7 is a schematic view showing one example of the core wirefor a guide wire according to the present invention.

[0031]FIG. 8 is a schematic view showing another example of the corewire for a guide wire according to the present invention.

[0032]FIG. 9 is a schematic view showing one example of the guide wireaccording to the present invention.

[0033]FIG. 10 is an enlarged cross-sectional view showing anotherexample of the guide wire according to the present invention.

[0034]FIG. 11 is a schematic view showing a further example of the guidewire according to the present invention.

[0035]FIG. 12 is an enlarged cross-sectional view showing a furtherexample of the guide wire according to the present invention.

[0036]FIG. 13 is an A-B cross-sectional view of FIG. 12.

[0037]FIG. 14 is a schematic view showing an example of a catheteraccording to the present invention.

[0038]FIG. 15 is an enlarged A-A′ cross-sectional view of FIG. 14.

[0039]FIG. 16 is a schematic view showing another example of a catheteraccording to the present invention.

[0040]FIG. 17 is an enlarged B-B′ cross-sectional view of FIG. 16.

[0041]FIG. 18 is an enlarged C-C′ cross-sectional view of FIG. 16.

[0042]FIG. 19 is a schematic view showing a further example of acatheter according to the present invention.

[0043]FIG. 20 is a schematic view showing a further example of a PTCAcatheter equipped with a balloon according to the present invention.

[0044]FIG. 21 is an enlarged D-D′ cross-sectional view of FIG. 20.

[0045]FIG. 22 is an enlarged E-E′ cross-sectional view of FIG. 20.

[0046]FIG. 23 is a schematic view showing another example of a catheteraccording to the present invention.

[0047]FIG. 24 is an enlarged F-F′ cross-sectional view of FIG. 23.

[0048]FIG. 25 is a schematic view showing a further example of acatheter according to the present invention.

[0049]FIG. 26 is an enlarged G-G′ cross-sectional view of FIG. 25.

[0050]FIG. 26 is an enlarged G-G′ cross-sectional view of FIG. 25.

[0051]FIG. 27 is a schematic view showing a further example of acatheter according to the present invention.

[0052]FIG. 28 is a partial enlarged cross-sectional view of FIG. 27.

[0053]FIG. 29 is a schematic view showing a further example of acatheter according to the present invention.

[0054]FIG. 30 is an enlarged H-H′ cross-sectional view of FIG. 29.

[0055]FIG. 31 is a schematic view showing a further example of acatheter according to the present invention.

[0056]FIG. 32 is an enlarged I-I′ cross-sectional view of FIG. 31.

DETAILED DESCRIPTION OF THE INVENTION

[0057] [1] Composition of the Functionally Graded Alloy

[0058] The functionally graded alloy of the present invention contains3-10 weight % of Al, 5-20 weight % of Mn, with the balance beingsubstantially Cu and inevitable impurities. Although the functionallygraded alloy has a β-phase structure [body-centered cubic (bcc)structure], at high temperatures a martensitic transformation withoutdiffusion occurs at low temperatures. Specifically, the β-phasestructure is changed to a dual-phase structure of an α-phase[face-centered cubic (fcc) structure] and a Heusler phase [orderedbody-centered cubic (fcc) structure] by heating at about 300° C.

[0059] When the aluminum content is less than 3 weight %, the beta-phasecannot be formed. On the other hand, when the aluminum content exceeds10 weight %, the resultant alloy becomes extremely brittle. Thepreferred aluminum content is 6-10 weight %, although it may be changeddepending on the amount of manganese.

[0060] The inclusion of manganese makes the range of the β-phase shifttoward a low aluminum region, thereby remarkably improving the coldworkability of the alloy, which makes it easy to form the alloy. Whenthe manganese content is less than 5 weight %, sufficient workabilitycannot be obtained, failing to form the region of the β-phase. On theother hand, when the manganese exceeds 20 weight %, sufficient shaperecovery properties cannot be obtained. The preferred manganese contentis 8-12 weight %.

[0061] The Cu—Al—Mn alloy having the above composition have a good hot-and cold-workability, achieving a cold working ratio of 20 to 90% ormore. This enables the formation of extremely thin wires, sheets, pipes,etc., which has conventionally been difficult.

[0062] In addition to the above components, the functionally gradedalloy of the present invention may further contain at least one elementselected from the group consisting of Ni, Co, Fe, Ti, V, Cr, Si, Nb, W,Sn, Ag, Mg, P, Zr, Zn, B, and misch metals. These elements act to makecrystal grains fine while maintaining the cold workability of thefunctionally graded alloy, thereby improving the strength of the alloy.The total content of these additional elements is preferably 0.001-10weight %, particularly 0.001-5 weight %. When the total content of theseelements exceeds 10 weight %, the martensitic transformation temperatureof the alloy lowers, making the β-phase structure unstable.

[0063] Ni, Co, Fe and Sn are elements which are effective forstrengthening the matrix structure of the alloy. The preferred contentis 0.001-3 weight % for each of Ni and Fe. Although Co acts to make thecrystal grains fine by the formation of Co—Al, an excess amount of coreduces the toughness of the alloy. Thus, the preferred content of Co is0.001-2 weight %. Additionally, the preferred content of Sn is 0.001-1weight %.

[0064] Ti is combined with harmful elements such as N and O to formoxynitrides. When Ti is added together with B, they form borides whichfunction to make the crystal grains fine, thereby improving the shaperecovery ratio of the alloy. The preferred Ti content is 0.001-2 weight%.

[0065] V, Nb, Mo and Zr increase the hardness of the alloy, therebyimproving the wear resistance of the alloy. Because these elements arenot substantially dissolved in the matrix, they are deposited as bcccrystals, effective in making th3e crystal grains fine. The preferredcontent of each of V, Nb, Mo and Zr is 0.001-1 weight %.

[0066] Cr is effective in maintaining the wear resistance and thecorrosion resistance of the alloy. The preferred Cr content is 0.001-2weight %.

[0067] Si increases the corrosion resistance of the alloy. The preferredSi content is 0.001-2 weight %.

[0068] W improves the deposition strengthening of the alloy because W isnot substantially dissolved in the matrix. The preferred W content is0.001-1 weight %.

[0069] Mg removes harmful elements such as N and O and fixes harmfulelements sulfur as sulfides, thereby improving the hot workability andthe toughness of the alloy. However, and excess of Mg causes grainboundary segregation, thereby making the alloy brittle. The preferred Mgcontent is 0.001-0.5 weight %.

[0070] P acts as a deoxidizer, improving the toughness of the alloy. Thepreferred P content is 0.01-0.5 weight %.

[0071] Zn lowers the shape memory treatment temperatures. The preferredZn content is 0.001-5 weight %.

[0072] B, which makes the crystal grains fine, is preferably usedtogether with Ti and Zr. The preferred B content is 0.01-0.5 weight %.

[0073] Misch metals make the crystal grains fine. The preferred contentsof misch metals is 0.001-2 weight %.

[0074] [2] Production of Functionally Graded Alloy

[0075] a. Forming Copper-based Alloy

[0076] A melt of copper-based alloy having the composition 3-10 weight %of Al, 5-20 weight % of Mn, with the balance being substantially Cu andinevitable impurities is cast and formed into a desirable shape by hotrolling, cold rolling, pressing, etc. The alloy of the present inventionhas good hot and cold workability, achieving a cold working ratio of 20to 90% or more. This enables the formation of extremely thin wires,sheets, ribbons, pipes, etc., which conventionally is difficult.

[0077] In the case of a copper-based alloy containing 8-10 weight % ofaluminum, an α+β dual-phase structure having excellent workability isformed when the average cooling speed after hot working is 200° C. perminute or less. The copper-based alloy is desirably cooled to the abovespeed, particularly in a range of 800-400° C. If the cooling speed isfaster than this speed, the β-phase is mainly formed in the alloy, whichfails to obtain as high a workability as when the α+β dual phase isformed. On the other hand, in the case of a copper-based alloycontaining 3-8 weight % of aluminum, the copper-based alloy may becomposed only of a β-phase structure after hot working, and the coolingspeed after hot working is not limited.

[0078] b. Solution Treatment

[0079] The copper-based alloy is then subjected to heat treatment(solution treatment) at 500° C. or more, preferably 600-900° C., totransform its crystal structure to the β-phase. After heat treatment,the β-phase is frozen by rapid cooling at a rate of 50° C. per second ormore. The rapid cooling of the alloy is carried out by immersing thealloy in a cooling medium such as water, or by forced-air cooling. Whenthe cooling speed is less than 50° C. per second, the a-phase depositsin the alloy, failing to maintain the alloy in a state having onlyβ-phase crystal structure, and thus reducing the property gradient. Thepreferred cooling speed is 200° C. per second or more.

[0080] c. Aging Treatment

[0081] According to the present invention, the aging treatment of thefirst portion wherein the β-phase crystal structure is maintained iscarried out at a temperature of less than 250° C. The aging treatment ofthe second portion in which the crystal structure is transformed intothe dual-phase structure of the α-phase and the Heusler phase is carriedout at 250-350° C. The aging treatment of the third portion between thefirst and second portions is carried out at a continuous or stepwisetemperature gradient (temperature distribution) from the heatingtemperature of the first portion to that of the second portion.

[0082] To meet the above conditions, the aging treatment is preferablycarried out in a gradient temperatures heater. FIG. 1 is a schematicview showing an example of such a gradient temperature heater. Thegradient temperature heater 1 for the aging treatment of a functionallygraded alloy rod 7 comprises a furnace pipe 2, a nichrome wire 3 woundaround the furnace pipe 2, a heat-insulating member 4, a plurality oftemperature sensors 51, 52, 53, and a power supply/temperaturecontroller 6 connected to the nichrome wire 3 and the temperaturesensors 51, 52, 53. In this example, the density gradient of the woundnichrome wire 3 controls the temperature gradient in the furnace pipe 2.To turn one end portion 71 of the alloy rod 7 to a first portioncomposed essentially of a β-phase, the nichrome wire 3 is wound sparselyaround one end portion 21 of the furnace pipe 2. Also, to turn the otherend portion 72 of the alloy rod 7 to a second portion composedessentially of an α-phase and a Heusler phase, the wire 3 is wounddensely around the other end portion 22 of the furnace pipe 2. Thus, thefurnace pipe 2 has a temperature gradient which may be controlled by thepower supply/temperature controller 6.

[0083] The heating temperature of the first portion is less than 250°C., preferably 100-200° C. If the heating temperature of the firstportion were too low, the β-phase would be unstable, making it likelythat the martensitic transformation temperature will change when thealloy is left at room temperature. On the other hand, when the heatingtemperature is 250° C. or more, the α-phase may be deposited, and thusthe difference in properties between the firsts and second portions willnot be increased.

[0084] The heating temperature of the second portion is 250-350° C.,preferably 280-320° C. When it is less than 250° C., the crystalstructure of the second portion is not sufficiently transformed into adual-phase structure of an α-phase and a Heusler phase, with a failureto increase the difference in properties between the first and secondportions. On the other hand, when it is more than 350° C., the crystalstructure becomes coarse, and properties such as yield stress, hardnessand the like become coarse.

[0085] The difference in heating temperature between the first andsecond portion is preferably 50° C. or more, particularly 80° C. ormore. When it is less than 50° C., the difference in properties betweenthe first and second portions becomes smaller.

[0086] The aging treatment time in general is preferably 1-300 minutes,particularly 5-200 minutes, although this time may vary depending uponthe composition of the functionally graded alloy. Less than one minuteof aging would not provide sufficient aging effects. On the other hand,when the aging time is more than 300 minutes, the alloy structurebecomes too coarse to keep sufficient mechanical properties in thefunctionally graded material.

[0087] In the case of a core wire for a guide wire, the copper-basedalloy core wire may be subjected to an aging treatment in the followingtwo ways: The first aging treatment is to heat the core wire uniformlyat 250° C. or less, preferably 100-200° C., such that the core wire hasuniform shape recovery properties and superelasticity.

[0088] The second aging treatment is to heat the core wire at differenttemperatures, such that the core wire has gradient properties. Namely,the core wire has a high-rigidity body portion, a low-rigidity tip endportion, and an intermediate portion between them having rigiditydecreasing from the high-rigidity body portion to the low-rigidity tipend portion. The high-rigidity body portion is obtained with an agingtreatment at 250-350° C., preferably 280-320° C., and the low-rigiditytip end portion is obtained by an aging treatment at less than 250° C.,preferably 100-200° C. The intermediate portion between the body portionand the tip end portion is obtained by an aging treatment at atemperature continuously or stepwise changing from the high-rigiditybody portion to the low-rigidity tip end portion. The difference inaging temperature between the high-rigidity body portion and thelow-rigidity top end portion is preferably 50° C. or more, particularly80° C. or more.

[0089] [3] Properties of Functionally Graded Alloy

[0090] (a) Crystal Structure

[0091] The functionally graded alloy of the present invention comprisesa first portion composed essentially of a β-phase, a second portioncomposed essentially of an α-phase and a Heusler phase, and a thirdportion having a crystal structure continuously or stepwise changingfrom the first portion to the second portion.

[0092] The term “composed essentially of a β-phase” as used herein meansnot only a crystal structure consisting only of a β-phase, but also acrystal structure containing, in addition to the β-phase, other phasessuch as an β-phase, a Heusler phase, borides such as TiB and ZrB, bccphases of V, Mo, Nb and W, and intermetallic compounds such as NiAl,CoAl, etc. in such small percentages so as not to affect thesuperelasticity and shape recovery properties of the first portion. Thetotal amount of the α-phase and the Heusler phase is preferably 5 volume% or less. When it exceeds 5 volume %, the superelasticity and shaperecovery properties of the first portion are remarkably decreased,thereby making the gradient of the properties smaller.

[0093] Also, the term “composed essentially of a dual phase comprisingan α-phase and a Heusler phase” as used herein means not only a crystalstructure consisting of only the α-phase and the Heusler phase, but alsoa crystal structure containing, in addition to the α-phase and theHeusler phase, other phases such as β-phase, borides such as TiB andZrB, bcc phases of V, Mo, Nb, and W, and intermetallic compounds such asNiAl, CoAl, etc. in such small percentages as not to affect the hardnessof the second portion. The amount of the β phase is preferably 10 volume% or less in the second portion.

[0094] The term “continuously or stepwise changing crystal structure” asused herein means that a volume ration of the β-phase to [the α-phaseand the Heusler phase] changes continuously or stepwise in the crystalstructure. The α-phase and the Heusler phase may be gradually depositedfrom the β-phase by aging treatment. The higher the aging temperature,and the longer the aging time, the more the α-phase an the Heusler phaseare deposited. Whether the crystal structure changes continuously orstepwise in the third portion depends upon the aging temperaturedistribution and the aging time. When the aging treatment is carried outat a stepwise temperature distribution for a short period of time, theresultant crystal structure changes stepwise. The boundaries between thefirst and third portions and between the second and third portions arenot explicit in the case of the third portion having a continuouslychanging crystal structure. Because the properties change generallysharply in the third portion, however, the boundaries of the above threeportions can relatively easily be determined from the distribution ofproperties.

[0095] The first portion composed essentially of the β-phase has shapememory properties and superelasticity as described in Japanese Laid-OpenPatent No. 7-62472. In contrast thereto, the second portion is composedof a hard material which is resistant to bending and which hascompletely different properties from the first portion. Although thedistance between the first portion and the second portion (i.e., lengthof the third portion) may arbitrarily be set, it is preferably about 2cm of more, particularly about 5 cm or more. It is difficult to providethe ageing temperature gradient in a distance of less than 2 cm.

[0096] (b) Differences in Properties

[0097] With respect to some properties, differences between the firstportion and the second portion will be described in detail below.

[0098] (i) Hardness

[0099] The first portion preferably has a hardness of less than 350 Hv,and the difference in hardness between the first portion and the secondportion can be made as large as 20 Hv or more. However, the hardness ofthe alloy may vary within the above range, depending upon itscomposition.

[0100] (ii) Yield Stress

[0101] Because the first portion which is composed essentially of aβ-phase which has superelasticity, the yield stress (0.2% offset yieldstrength) of the first portion is less than 400 Mpa, although it mayvary within the range depending upon the composition of the alloy. Thedifference in yield stress between the first portion and the secondportion can be made as large as 50 Mpa or more.

[0102] (iii) Shape Recovery Ratio

[0103] The first portion has excellent shape recovery properties,exhibiting a shape recovery ratio of 80% or more. The shape recoveryration of the second portion is as low as less than 15%, which meansthere are substantially no shape recovery properties. The difference inshape recovery ratio between the first and second portions can be madeas large as 70% or more.

[0104] [iv] Core Wire for Guide Wire

[0105] The core wire for a guide wire comprises a functionally gradedcopper-based alloy wire having at least a low-rigidity tip end portionand a high-rigidity body portion.

[0106] First embodiment

[0107] In the first embodiment, as shown in FIG. 7, the core wire is astraight copper-based alloy wire having a tip end portion that is nottapered. The core wire 2 is composed of four regions, 2 a, 2 b, 2 c, and2 d, from the base end 3 to the tip end 4. Each region 2 a, 2 b, 2 c,and 2 d has rigidity which decreases stepwise from the side of the baseend 3 to the side of the tip end 4. Each region may have an arbitrarilyset length.

[0108] A gradient-rigidity core wire as shown in FIG. 7 many be formedas described above by hot working and/or cold working, maintaining thetemperature of the wire above 500° C. and rapidly quenching the wire,and further aging the wire at different temperatures in the respectiveregions 2 a, 2 b, 2 c, and 2 d. The aging temperature in region 2 a ispreferably 250-350° C. and the aging temperature in the region 2 d isless than 250C. The aging temperatures in regions 2 b and 2 c arebetween those for regions 2 a and 2 d, with the aging temperature inregion 2 b being higher than that for region 2 c.

[0109] Second embodiment

[0110] In the second embodiment, as shown in FIG. 8, the core wire is acopper-based alloy wire composed of four regions 2 a, 2 b, 2 c, and 2 dfrom the base end 3 to the tip end 4. Rigidity decreases in each region2 a, 2 b, 2 c, and 2 d from the side of the base end 3 to the side ofthe tip end 4. Each region may have an arbitrarily set length.

[0111] As in the first embodiment, region 2 a is a high-rigidity region,while region 2 d is a low-rigidity region. Regions 2 b and 2 c haveintermediate rigidity between that of regions 2 a and 2 d, with therigidity of region 2 b being higher than that of region 2 c. Becauseregion 2 d has a smaller diameter in the second embodiment than in thefirst embodiment, the softness of the copper-based alloy in region 2 dmay be less in the second embodiment than in the first embodiment. Thecore wire of the second embodiment may be produced in the same manner asin the first embodiment.

[0112] Third embodiment

[0113] In the third embodiment, shown in FIG. 9, the core wire comprisesa base wire 5 and a core wire 6 connected to each other. The core wire 6is a copper-based alloy wire, and the base wire 5 may be a flat ribbonmade of conventional material such as stainless steel. Ends of the basewire 5 and the core wire 6 are partially overlapped and bonded with acoil, etc.

[0114] The core wire 6 consists of two regions, 6 a and 6 b, from thebase end 7 a to the tip end 7 b. Region 6 a is a high-rigidity region,while region 6 b is a region having rigidity continuously decreasingtoward the tip end 7 b. The core wire 6 is soft (less rigid) andsuperelastic in the vicinity of tip end 7 b. Each region may have anarbitrarily set length.

[0115] As in the first embodiment, core wire 6 is provided with arigidity gradient by applying different aging temperature to differentregions The aging temperature of region 6 a is preferably 250-350° C.The aging temperature of region 6 b has a temperature distribution whichis continuously lowered from base end 7 a to tip end 7 b. The highesttemperature of the above temperature distribution is preferably the sameas in region 6 a, and the lowest temperature in region 6b is preferablylower than 250° C.

[0116] [5] Catheter

[0117] (a) Catheter Having Copper-based Alloy Pipe

[0118] One catheter according to the present invention is at leastpartially made of a copper-based alloy pipe. The catheter is relativelyrigid in a body portion, and has low rigidity in a tip end portion. Thebending modulus of the copper-based alloy pipe decreases continuously orstepwise in a direction from the base end to the tip end of thecatheter, and at least a tip end portion of the copper-based alloy pipehas superelasticity.

[0119] The following are specific embodiments of catheters of thepresent invention.

[0120] (i) First embodiment

[0121]FIG. 14 shows a first example of the catheter of the presentinvention, and FIG. 15 is an A-A′ cross-sectional view of FIG. 14.

[0122] The body of the catheter is made of a copper-based alloy pipe 42,which has a bending modulus which decreases continuously or stepwisefrom the base end 43 to the tip end portion 44. The copper-based alloypipe can be formed from a thicker pipe by gradually reducing the pipediameter by rolling or drawing.

[0123] Pipe 42 has a high-rigidity body portion 42 a, a low-rigidity,superelastic tip end portion 42 c, and an intermediate portion 42 bbetween them which has intermediate rigidity. In each region, therigidity may be uniform or gradually changing.

[0124] A gradient rigidity copper-based alloy pipe can be formed by hotworking and/or cold working, keeping the pipe at a temperature of atleast 500° C. and rapidly quenching the pipe, and then aging the pipe atdifferent temperatures in different regions. The aging treatmenttemperature is preferably 250-350° C. in body portion 42 a, and lessthan 250° C. in tip end portion 42 c. The aging treatment temperature inintermediate portion 42 b is between that of body portion 42 a and tipend portion 42 c. When a gradient is necessary in each region, the agingtreatment temperature should gradually decrease in a direction from baseend 43 to tip end 44 of the catheter in each region.

[0125] (ii) Second embodiment

[0126]FIG. 16 shows a second embodiment of a catheter according to thepresent invention. FIG. 17 is a B-B′ cross-sectional view of FIG. 16,and FIG. 18 is a C-C′ cross-sectional view of FIG. 16.

[0127] Catheter body 51 comprises a copper-based alloy pipe 52, whichhas a bending modulus which decreases continuously or stepwise from baseend 53 to tip end portion 54. Copper-based alloy pipe 52 can be formedfrom a thicker pipe by gradually reducing the pipe diameter by rollingor drawing. Catheter 51 may be the same as catheter 41 except that tipend portion 52 c is tapered.

[0128] (iii) Third embodiment

[0129]FIG. 19 shows a third embodiment of a catheter of the presentinvention. Catheter 61 is bent at an angle of 90-150° in a tip endposition 62 so that the catheter 61 can easily enter into a winding orbranched blood vessel. After bending, the copper-based alloy pipe issubjected to a solution treatment and an aging treatment.

[0130] (b) Catheter Having Copper-based Alloy Reinforcing Member

[0131]FIG. 23 shows a second type of catheter according to the presentinvention. FIG. 24 is an F-F′ cross-sectional view of FIG. 23. Thecatheter 101 comprises a flexible tube body 111, a hub 112 mounted on abase end of the flexible tube body 111, and a soft tip 113 mounted to atip end of the flexible tube body 111. The flexible tube body 111 ispreferably reinforced by wire- or ribbon-shaped reinforcing copper-basedalloy members 115.

[0132] In the embodiment shown in FIG. 24, the tube body 111 comprisesan inner layer 114, an intermediate Cu—Al—Mn alloy braid layer 115, andan outer layer 116. While the intermediate Cu—Al—Mn alloy braid 115 ismade of eight thin Cu—Al—Mn alloy wires in FIG. 24, there can be anynumber of thin wires forming the braid. Also, a plurality of straightcopper-based alloy wires may be disposed along the length of thecatheter 101. The copper-based alloy wires may be in the form of a coil.

[0133] The copper-based alloy reinforcing member has a bending moduluswhich either decreases continuously or stepwise from the base end to thetip end. Thus, the body portion is a high-rigidity region, the tip endportion is a low-rigidity, superelastic region, and the intermediateportion is a region which has a rigidity intermediate that of the bodyportion and the tip end portion. In each region, rigidity may be uniformor gradually changing.

[0134] The gradient-rigidity, reinforcing copper-based alloy member canbe obtained by aging different regions at different temperatures in thesame manner as described above.

[0135] A catheter containing a reinforcing metal member can be producedby co-extruding a resin for the tube body 111 and a reinforcing metalmember, or by immersing an inner layer 114 coated with the reinforcingmetal member 115 in a resin solution and solidifying the resin to forman outer layer 116.

[0136] [6] Surface Treatment

[0137] The copper-based alloy member such as core wires, guide wires andcatheters are preferably coated with Au, Pt, Ti, Pd or TiN by plating orvapor deposition. The copper-based alloy members are preferably coatedwith polyethylene, polyvinyl chloride, polyesters, polypropylene,polyamides, polyurethane, polystyrene, fluoroplastics, silicon rubbersor their elastomers, or composites thereof. These coating materialspreferably contain X-ray contrast media such as barium sulfate.Furthermore, surfaces of the cores wires, guide wires, and catheters arepreferably coated with lubricating materials such as polyvinylpyrrolidone, ethyl maleate, methyl vinyl ether-maleic anhydridecopolymer, etc.

[0138] The present invention will be described in detail below referringto the following EXAMPLES, without restricting the scope of the presentinvention as defined by the claims. These examples are for illustrationonly, and are not intended to limit the scope of the invention.

EXAMPLE 1 COMPARATIVE EXAMPLE 1

[0139] Copper-based alloys having compositions shown in Table 1 asSample Nos. 1-7 (Example 1) and Sample No. 8 (Comparative Example 1)were melted, and solidified at a cooling rate of 140° C./minute onaverage to form billets each having a diameter of 20 mm. Each billet wascold-drawn a plurality of times with intermediate annealing to produce awire having a diameter of 0.5 mm and a length of 200 mm. Each of theresultant wires was heat-treated at 900° C. for 15 minutes, rapidlyquenched by immersion in water with ice, and then subjected to an agingtreatment by a heater shown in FIG. 1 for 15 minutes, to obtain afunctionally graded alloy wire. The temperature distribution of theheater for the aging treatment is 140° C. in a low-aging temperatureregion and 300° C. in a high-aging temperature region, as shown in FIG.2. TABLE 1 Compositions of Functionally Graded Alloys Sample Elements(weight %) No. Cu Al Mn Others 1 Bal. 8.1 9.7 — 2 Bal. 8.7 10.6 — 3 Bal.8.7 10.8 Ti: 0.1, B: 0.05 4 Bal. 8.4 10.5 V: 0.26 5 Bal. 7.6 9.7 V: 0.456 Bal. 8.0 9.6 Ni: 1.0 7 Bal. 8.1 9.7 Co: 0.5 8 Bal. 8.0 9.5 Co: 2.4

[0140] Each wire thus aging-treated was measured with respect toproperties described below in a low-aging temperature porrtion and ahigh-aging temperature portion to determine property gradient thereof.

[0141] (i) Hardness

[0142] The hardness of each wire was measured both in a low-agingtemperature portion and a high-aging temperature protion by amicro-Vickers hardness tester. The measurement results are shown inTable 2.

[0143] (ii) Shape Recovery Ratio

[0144] Each wire was wound around a round rod having a diameter of 25 mmin liquid nitrogen, and measured with respect to a curvature radius R₀after taken out of the liquid nitrogen. The curved wire was then heatedto 200° C. to recover its original shape, and again measured withrespect to a curvature radius R₁. The shape recovery ratio Rs of thewire was calculated by the formula: Rs(%)=100×(R₁−R₀)/R₁. The calculatedshape recovery ratios Rs are shown in Table 2.

[0145] (iii) Tensile Test

[0146] Each wire was subjected to a tensile test according to JIS Z 2241to measure tensile strength, rupture elongation and yield strength (0.2%offset). The results are shown in Table 3. TABLE 2 Hardness and ShapeRecovery Ratio of Functionally Graded Alloys Shape Recovery Hardness(Hv) Ratio (%) Sample No. L* H* L* H* 1 240 350 83 0 2 270 380 88 0 3235 351 90 0 4 274 360 85 0 5 280 370 81 0 6 258 372 95 0 7 239 347 94 08 330 391 99 0

[0147] TABLE 3 Tensile Test Results of Functionally Graded AlloysTensile Strength Rupture 0.2% Offset Yield (MPa) Elongation (%) Strength(MPa) Sample No. L* H* L* H* L* H* 1 432 1129 15.4 3.2 50 807 2 699 107417.2 3.3 310 774 3 639 728 15.7 3.2 315 544 4 749 1147 18.2 4.6 240 7455 272 947 13.7 7.2 63 539 6 245 1032 18.2 2.7 212 783 7 529 894 17.3 3.6237 717 8 594 650 2.4 0.0 370 Broken

[0148] As is clear from Tables 2 and 3, the properties are remarkablydifferent between the low-aging temperature portion and the high-agingtemperature portion. For example, Sample No. 1 exhibits yield stress(0.2% offset yield strength), which is as low as 50 MPa in a low-agingtemperature portion and as high as 16 times or more in a high-agingtemperature portion. In Sample No. 8 (Comparative Example 1) containingan excess amount of Co, the toughness of the high-aging temperatureportion is remarkably deteriorated by the deposition of Co—Al, leadingto breakage.

[0149] The wire of Sample No. 3 was divided into ten equal parts, and acenter portion of each part was measured with respect to hardness. Theresults are plotted in FIG. 2. As is clear from FIG. 2, the hardnesscontinuously increased from the low-aging temperature portion to thehigh-aging temperature portion. Particularly in the vicinity of theaging temperature of 250° C., the hardness drastically changed. It wasconfirmed from the change of hardness that a region extending up toabout 7 cm from the low-aging temperature end had a crystal structuresubstantially composed of β-phase, and that a region extending up toabout 7 cm from the high-aging temperature end had a dual-phase crystalstructure composed essentially of an α-phase and a Heusler phase. In theintermediate region extending 6 cm between the low-aging temperatureregion and the high-aging temperature region, the crystal structure wasgradually changing.

[0150] The wire of Sample No. 1 was observed by an optical microscope inboth low-aging temperature portion and high-aging temperature portion.FIG. 3 is an optical photomicrograph showing the microstructure of thelow-aging temperature portion of the functionally graded alloy of SampleNO. 1. As a result of electron diffraction analysis, it was confirmedthat the crystal structure of the low-aging temperature portion wascomposed essentially of a β-phase. FIG. 4 is an optical photomicrographshowing the microstructure of high-aging temperature portion of thefunctionally graded alloy of Sample No. 1. It was also confirmed byelectron diffraction that the microstructure of the high-agingtemperature portion was a dual-phase structure of an β-phase and aHeusler phase.

[0151] As a result of X-ray diffraction analysis of Sample No. 1, it wasconfirmed that the low-aging temperature portion was composed of 100volume % of a β-phase, with 0 volume % of an α-phase and a Heuslerphase. It was also confirmed that the high-aging temperature portion wascomposed of 65 volume % of an α-phase and 35 volume % of a Heuslerphase, with a β-phase substantially 0 volume %.

EXAMPLE 2

[0152] Copper-based alloys having compositions shown in Table 1 asSample Nos. 2 and 3 were formed into wires each having a diameter of 0.5mm and rapidly cooled in the same manner as in Example 1. The resultantcopper-based alloy wires were then subjected to an aging treatment at150° C., 200° C., 250° C., 300° C., 350° C. and 400° C., respectively,each for 15 minutes. The hardness of the aged copper-based alloy wireswas measured in the same manner as in Example 1 and plotted in FIG. 5.

[0153] As is clear from FIG. 5, the hardness of the copper-based alloysrapidly increased when the aging temperature exceeded 250° C. However,the hardness of the copper-based alloys remarkably decreased when theaging temperature exceeded 350° C.

EXAMPLE 3

[0154] Copper-based alloys having compositions shown in Table 1 asSample Nos. 5 and 6 were formed into wires each having a diameter of 0.5mm and rapidly cooled in the same manner as in Example 1. The resultantcopper-based alloy wires were subjected to an aging treatment at 300° C.for 5, 15, 60, 200, 700, 4500 and 10000 minutes, respectively. Thehardness of the aged copper-based alloy wires was measured in the samemanner as in Example 1 and plotted in FIG. 6.

[0155] As is clear from FIG. 6, in Sample No. 5 containing V and SampleNo. 6 containing Ni, the highest hardness was obtained for an aging timeof 5-700 times.

EXAMPLE 4

[0156] A copper-based alloy wire as shown in FIG. 7 was produced toprovide a core wire 2 for a guide wire. The core wire 2 ha da totallength of 1200 mm, and its tip end 4 was not tapered.

[0157] For this purpose, a copper-based alloy comprising 7.5 weight % ofAl, 9.9 weight % of Mn, 2.0 weight % of Ni, and 80.6 weight % of Cu wasmelted, solidified at a cooling speed of 140° C./min. on average, andthen cold-drawn to provide a wire of 0.4 mm in diameter. Thereafter, thewire was heat-treated at 900° C. for 10 minutes and rapidly quenched byimmersion in ice water.

[0158] The resultant core wire 2 was cut to 1200 mm, and subjected to anaging treatment at different temperatures in four regions from the baseend 3 to the top end 4 for 15 minutes; at 300° C. in a region 2 a of 600mm, at 250° C. in a region 2 b of 300 mm, at 200° C. in a region 2 c of200 mm, and at 150° C. in a region 2 d of 100 mm, respectively. Withthis heat treatment, the rigidity of the core wire 2 decreased from thebased end 3 to the tip end 4. The hardness of each region was measuredby a micro-Vickers hardness tester. The measurement results are shown inTable 4. TABLE 4 Hardness distribution Region Hardness (Hv) 2a 330 2b290 2c 240 2d 235

[0159] It has been found that the Cu—at least—Mn alloy composing thecore wire 2 can be provided with different properties at as smallintervals as a few centimeters by heating conditions of the agingtreatment. Thus, without tapering, a good balance of rigidity andsoftness can be achieved continuously along the core wire 2. Also, thecore wire 2 is an integral wire made of an alloy of the samecomposition, which is excellent in torque conveyance.

EXAMPLE 5

[0160] A guide wire 11 was produced by using a copper-based alloy wireas shown in FIG. 10 as a core wire 12. The core wire 12 comprising fourregions 12 a (500 mm), 12 b (100 mm), 12 c (50 mm) and 12 d (50 mm) fromthe base end 13 to the tip end 14 was tapered from region 12 c to thetip end 14, such that regions 12 a, 12 b had a diameter of 0.4 mm, andthat the tip end 14 had a diameter of 0.1 mm. The core wire 12 wassubjected to the same aging treatment as in Example 4 under thefollowing aging conditions: at 300° C. for region 12 a, at 250° C. forregion 12 b, at 200° C. for region 12 c, and at 150° C. for region 12 d.The aging time was 15 minutes. With this aging treatment, the rigidityof the core wire 12 decreased from the base end 13 to the tip end 14.

[0161] The resultant core wire 12 was plated with gold, and coated witha polyamide elastomer layer 15 containing 40 weight % of barium sulfateas an X-ray contrast medium. Further, to improve lubrication at the timeof insertion into the blood vessel, a surface of the coating layer 15was covered by a lubricating layer 17 based on polyvinyl pyrrolidone.

EXAMPLE 6

[0162] A guide wire 21 as shown in FIG. 11 was produced. A core wire 22comprising four regions 22 a (500 mm), 22 b (100 mm), 22 c (50 mm) and22 d (50 mm) from the base end 23 to the tip end 24 was tapered fromregion 22 c to the tip end 24, such that regions 22 a, 22 b had adiameter of 0.4 mm, and that the tip end 24 had a diameter of 0.1 mm.The core wire 22 was subjected to the same aging treatment as in Example4 under the following aging conditions: at 300° C. for region 22 a, at250° C. for region 22 b, at 200° C. for region 22 c, and at 150° C. forregion 22 d. The aging time was 15 minutes. With this aging treatment,the rigidity of the core wire 22 decreased from the base end 23 to thetip end 24.

[0163] The tapered portion of the resultant core wire was covered by acoil 26, and the tip end 24 was provided with a expanded portion 27 by aplasma welding to avoid damaging of the blood vessel walls. The corewire 22 and the coil 26 were plated with gold. To improve lubrication atthe time of insertion into the blood vessel, a surface of the goldplating was covered by a lubricating layer (not shown) based onpolyvinyl pyrrolidone.

EXAMPLE 7

[0164] A core wire 32 of a guide wire 31 as shown in FIG. 12 was abraided wire made of three thin copper-based alloy wires. See FIG. 13,an A-B cross section of FIG. 12. The core wire 32 had rigidity stepwisedecreasing along a region 32 a (500 mm), a region 32 b (100 mm) and aregion 32 c (50 mm) from the base end 33 to the tip end 34. The corewire 32 was tapered from region 32 c to the tip end 34, such that adiameter was 0.4 mm in regions 32 a, 32 b and 0.1 mm at the tip end 34.The tip end 34 was provided with an expanded portion 36 by a plasmawelding to avoid loosening of the braided wires and to improve the X-raycontrast of the tip end 34.

[0165] The core wire 32 was subjected to the same aging treatment as inExample 4 except for the following aging conditions: at 300° C. forregion 32 a, at 250° C. for region 32 b, and at 200° C. for region 32 c.The aging time was 15 minutes. With this aging treatment, the rigidityof the core wire 32 decreased from the base end 33 to the tip end 34.

[0166] The resultant core wire 32 was coated with a polyamide elastomerlayer 35 containing 40 weight % of barium sulfate as an X-ray contrastmedium. Further, to improve lubrication at the time of insertion intothe blood vessel, a surface of the coating layer 35 was covered by alubricating layer (not shown) based on polymethyl vinyl ether-maleicanhydride derivative.

EXAMPLE 8

[0167] A catheter as shown in FIG. 14 and 15 was produced. The catheter41 comprised a superelastic Cu—Al—Mn alloy pipe 42 having an outerdiameter of 1.5 mm and an inner diameter of 1.4 mm. The pipe 42 had abending modulus decreasing stepwise from a body portion 42 a to a tipend portion 42 c through an intermediate portion 42 b, and the tip endportion 42 c became gradually softer toward the tip end 44.

[0168] For this purpose, a copper-based alloy comprising 7.5 weight % ofAl, 9,9 weight % of Mn, 2.0 weight % of Ni, and 80.6 weight % of Cu wasmelted, solidified at a cooling speed of 140° C./min. on average, andthen cold-rolled to provide a pipe of 2 mm in diameter and 0.1 mm inthickness. Thereafter, the pipe was heat-treated at 900° C. for 10minutes and rapidly quenched by immersion in ice water.

[0169] The resultant pipe 42 was subjected to an aging treatment atdifferent temperatures in three regions for 15 minutes; at 300° C. in aregion 42 a, at 250° C. in a region 42 b, and at a temperature graduallydecreasing from 200° C. to 150° C. in a region 42 b, and at atemperature gradually decreasing from 200° C. to 150° C. in a region 42c, respectively. The pipe 42 was coated with a polyamide elastomer layer46 containing 40 weight % of barium sulfate as an X-ray contrast mediumand then with a polyvinyl pyrrolidone-based lubricating layer (notshown).

[0170] The resultant catheter 41 was rigid in a body portion 42 a andfully soft in a tip end portion 42 c, making sure safe use for practicalapplications. It is also possible to improve softness in the tip endportion 42 c without tapering. Particularly in a microcatheter having asmall diameter, its inner bore can be made relatively large, ensuringeasy and safe injection of X-ray contrasting medium, etc.

EXAMPLE 9

[0171] A catheter as shown in FIGS. 16-18 was produced. The catheter 51was constituted by a superelastic Cu—Al—Mn—V alloy pipe 52 having anouter diameter of 1.5 mm and an inner diameter of 1.4 mm. The pipe 52had bending modulus decreasing stepwise from a body portion 52 a to atip end portion 52 c through an intermediate portion 52 b, and the tipend portion 52 c was tapered such that it became gradually softer towardthe tip end.

[0172] For this purpose, a copper-based alloy comprising 7.5 weight % ofAl, 9.9 wieght % of Mn, 2.0 weight % of V, and 80.6 weight % of Cu wasmelted, solidified at a cooling speed of 140° C./min. on average, andthen cold-rolled to provide a pipe of 2 mm in diameter and 0.1 mm inthickness. Thereafter, the pipe was heat-treated at 900° C. for 10minutes and rapidly quenched by immersion in ice water.

[0173] The resultant pipe 52 was subjected to an aging treatment atdifferent temperatures in three regions for 15 minutes; at 300° C. in aregion 52 a, at 250° C. in a region 52 b, and at 150° C. in a region 52c, respectively. The pipe 52 was then coated with a polyamide elastomerlayer 56 containing 40 weight % of barium sulfate as an X-ray contrastmedium. The pipe 52 was provided with a soft tip 54 at the tip end toprevent the blood vessel walls from being damaged at the time ofinsertion. Like in Example 8, the pipe 52 was coated with a polyvinylpyrrolidone-based lubricating layer (not shown) from the intermediateportion 52 b to the tip end to increase lubrication at the time ofinsertion into the blood vessel.

[0174] The resultant catheter 51 was rigid in the body portion 52 a andfully soft in the tip end portion 52 c, making sure safe use forpractical applications. Because this catheter 51 has properties changingfrom the body portion 52 a to the tip end portion 52 c, and because thetip end portion 52 c is tapered toward the tip end, it has wideversatility in design with a rigid body portion and a soft tip endportion.

EXAMPLE 10

[0175] A catheter as shown in FIG. 19 was produced in the same manner asin Example 9. The catheter 61 was the same as in Example 9 except that atip end portion 62 of the catheter 61 was bent at about 120°, Thiscatheter 61 could easily be inserted into winding or branched bloodvessels.

EXAMPLE 11

[0176] A PTCA catheter 71 equipped with a balloon as shown in FIGS.20-22 was produced from the same Cu—Al—Mn—Ni alloy as in Example 8 inthe same manner as in Example 9. The catheter 71 comprised a Cu—Al—Mn—Nialloy pipe 72 having a diameter of 2 mm and a thickness of 0.1 mm. Thepipe 72 had rigidity decreasing stepwise from a body portion 72 a to atip end portion 72 c through an intermediate portion 72 b, and the tipend portion 72 c was tapered to become gradually softer toward the tipend.

[0177] The resultant pipe 72 was plated with gold and covered by apolyamide elastomer tube 73 in the tip end portion 72. The elastomertube 73 had a through-hole 76 for allowing a balloon 75 to inflate, anda through-hole 77 extending from a halfway of the catheter 71 to the tipend portion for allowing a guide wire to pass through. Because theCu—Al—Mn alloy pipe 72 extends almost up to a balloon region along thecatheter 71, the catheter 71 has full rigidity while showing excellentsoftness and kink resistance, ensuring safe use.

EXAMPLE 12

[0178] A catheter as shown in FIGS. 23 and 24 was produced. The catheter101 was constituted by a tube body 111, a hub 112 mounted to a base endof the tube body 111, and a soft tip 113 mounted to a tip end of thetube body 111. The tube body 111 was constituted by an inner layer 114,an intermediate Cu—Al—Mn alloy braid layer 115, and an outer layer 116as shown in FIG. 24. The intermediate Cu—Al—Mn alloy braid 115 was madeof eight 0.035-mm-thick Cu—Al—Mn alloy wires comprising 7.5 weight % ofAl, 9.9 weight % of Mn, 2.0 weight % of Ni, and 80.6 weight % of Cu. Thethin Cu—Al—Mn alloy wires were produced in the same manner as in Example9 The Cu—Al—Mn alloy braid 115 was coextruded with nylon 12 to form thecatheter 101 having the Cu—Al—Mn alloy braid 115 embedded in the tubebody 111.

EXAMPLE 13

[0179] A catheter as shown in FIGS. 25 and 26 was produced. The catheter102 comprised a tube body 121, a hub 122 mounted to a base end of thetube body 121, and soft tip 123 mounted to a tip end of the tube body121. The tube body 121 comprised an inner layer 124, an intermediateCu—Al—Mn alloy braid layer 125, and an outer layer 126 as shown in FIG.26. The intermediate Cu—Al—Mn—V alloy braid 125 comprised 32 thinCu—Al—Mn—V alloy wires having a thickness of 0.02 mm comprising 8.0weight % of Al, 10.2 weight % of Mn, 1.0 weight % of V, and 80.8 weight% of Cu. The Cu—Al—Mn—V alloy braid 125 was subjected to an agingtreatment at 300° C. in a region a, at 250° C. in a region b and at 150°C. in a region c for 15 minutes, so that the regions a, b and c hadrigidity decreasing in this order. The Cu—Al—Mn—V alloy braid 115 wascoextruded with a polyurethane resin in the same manner as in Example 12to form a catheter 102 having the Cu—Al—Mn—V alloy braid 125 embedded inthe tube body 121.

EXAMPLE 14

[0180] A catheter as shown in FIGS. 27 and 28 was produced. The catheter103 comprised a tube body 131, a hub 132 mounted to a base end of thetube body 131, and a soft tip 133 mounted to a tip end of the tube body131. The tube body 131 comprised an inner layer 134, an intermediateCu—Al—Mn—V alloy braid layer 135, and an outer layer 136 as shown inFIG. 28. The intermediate Cu—Al—Mn—V alloy braid 135 comprised twospirally crossing Cu—Al—Mn—V alloy ribbons each having a thickness of0.01 mm comprising 8.0 weight % of Al, 10.2 weight % of Mn, 1.0 weight %of V, and 80.8 weight % of Cu. The Cu—Al—Mn—V alloy braid 135 wassubjected to an aging treatment at temperatures shown in Table 5 belowfor 15 minutes so that regions d, e, f and g had rigidity decreasing inthis order. The hardness of the braid 135 in each region was measured bya micro-Vickers hardness tester. The measurement results are shown inTable 5. TABLE 5 Region Aging Temperature (° C.) Hardness (Hv) d 300 380e 250 290 f 200 260 g 150 270

[0181] The Cu—Al—Mn—V alloy braid 135 was coextruded with nylon 12 inthe same manner as in Example 12 to form a catheter 103 having theCu—Al—Mn—V alloy braid 135 embedded in the tube body 131.

EXAMPLE 15

[0182] A catheter as shown in FIGS. 29 and 30 was produced. The catheter104 comprised a tube body 141, a hub 142 mounted to a base end of thetube body 141, and a soft tip 143 mounted to a tip end of the tube body141. The tube body 141 comprised an inner layer 144, four intermediatewires 145 made of the same Cu—Al—Mn—V alloy as in Example 13, and anouter layer 146. The Cu—Al—Mn—V alloy wires 143 were subjected to anaging treatment at 300° C. in a region h, at 250° C. in a region i andat 150° C. in a region j for 15 minutes, so that the regions h, i and jhad rigidity decreasing stepwise in this order. Also, the catheter 104was tapered from a halfway of the region i to the tip end to ensuresoftness.

EXAMPLE 16

[0183] A catheter as shown in FIGS. 31 and 32 was produced in the samemanner as in Example 13. The catheter comprised a tube body 152, aY-shaped hub 152 mounted to a base end of the tube body 151, and aballoon 154 mounted to a tip end of the tube body 151. The tube body 151had a hole 157 for inflating the balloon 154, a thin Cu—Al—Mn alloy wire155 and an outer layer 156. The Cu—Al—Mn alloy wire 155 was subjected toan aging treatment at 300° C. in region k, at 250° C. in region 1 and at150° C. in region m for 15 minutes, so that regions k, 1 and m hadrigidity decreasing stepwise in this order. Also, the catheter 105 wastapered from a halfway of region m to the tip end to ensure softness.

[0184] As described above in detail, the functionally graded alloy ofthe present invention exhibits drastically changing properties such asshape recovery properties, superelasticity, hardness, mechanicalstrength, etc., without mechanical working such as cutting or chemicaltreatment such as etching for imparting size gradient. Such afunctionally graded alloy can be easily produced at low cost from acopper-based alloy composed essentially of a β-phase, by aging treatmentin a heater having a continuous or stepwise temperature gradient. Thefunctionally graded alloy of the present invention can be formed intovarious shapes because of its excellent cold workability.

[0185] When the core wire, the guide wire or the catheter comprises acopper-based alloy having gradient properties according to the presentinvention, it is provided with optimum rigidity and toughness in thebody portion and proper softness in the tip end portion withoutmechanical or chemical working. Such core wire, guide wire or catheteris excellent in insertion operability and torque conveyance, and can beinserted and placed at a desired spot in the blood vessel withoutdamaging the walls thereof.

What is claimed is:
 1. A core wire for a guide wire comprising a bodyportion having a high rigidity and a tip end portion having a rigiditylower than the rigidity of the body portion, wherein at least part ofsaid core wire is made of a copper-based alloy comprising 3-10 weight %of Al and 5-20 weight % of Mn, the balance being substantially Cu andinevitable impurities.
 2. The core wire for a guide wire according toclaim 1 wherein said copper-based alloy wire is formed by at least oneof hot-working and cold-working, maintained at a temperature of at least500° C. and rapidly quenched, and then aged at a temperature of not morethan 200° C. such that the core wire has shape recovery properties andsuperelasticity.
 3. The core wire for a guide wire according to claim 1wherein said copper-based alloy wire comprises a high-rigidity bodyportion, a low-rigidity tip end portion, and an intermediate portionbetween said high-rigidity body portion and said low-rigidity tip endportion, said intermediate portion having rigidity continuously orstepwise decreasing from said high-rigidity body portion to saidlow-rigidity tip end portion.
 4. The core wire for a guide wireaccording to claim 1 wherein said copper-based alloy wire is formed byhot working and cold working, maintained at a temperature of at least500° C. and then rapidly quenched, and further subjected to an agingtreatment comprising heating the high-rigidity body portion at atemperature of 250-350° C., heating the tip end portion at a temperatureof less than 250° C., and an intermediate portion, and heating anintermediate portion between said body portion and said tip end portionat a temperature continuously or stepwise changing from the heatingtemperature of said body portion to the heating temperature of the tipend portion.
 5. A guide wire comprising the core wire according toclaim
 1. 6. The guide wire according to claim 5 wherein said core wireis coated with a coating selected from the group consisting of Au, Pt,Ti, Pd, and TiN, and optionally with a resin.
 7. A catheter at leastpartially comprising a metal pipe, said metal pipe being made in atleast a tip end portion thereof of a copper-based alloy comprising 3-10weight % Al and 5-20 weight % Mn, the balance being substantially Cu andinevitable impurities.
 8. The catheter according to claim 7 wherein saidmetal pipe has a bending modulus which decreases continuously orstepwise in a direction from a base end to a tip end of the catheter. 9.The catheter according to claim 7 wherein said metal pipe is formed byat least one of hot working and cold working, maintained at atemperature of at least 500° C. and rapidly quenched, and then subjectedto an aging treatment at a temperature distribution that decreasescontinuously or stepwise in a direction from a base end to a tip end ofthe catheter, wherein the highest temperature is 250-350° C. and thelowest temperature is less than 250° C. in said temperaturedistribution.
 10. The catheter according to claim 7 wherein said metalpipe has an outer diameter which is at least partially decreasingcontinuously or stepwise in a direction from a base end to a tip end ofsaid catheter.
 11. The catheter according to claim 7 wherein said metalpipe is coated with a coating selected from the group consisting of Au,Pt, Ti, Pd, and TIN and optionally a resin.
 12. A catheter containing areinforcing metal member in at least part of a catheter tube, saidreinforcing metal member being made of a copper-based alloy comprising3-10 weight % Al and 5-20 weight % Mn, the balance being substantiallyCu and inevitable impurities.
 13. The catheter according to claim 12wherein said reinforcing metal member has a bending modulus whichdecreases continuously or stepwise in a direction from a base end to atip end of the catheter.
 14. The catheter according to claim 12 whereinsaid reinforcing metal member is formed by at least one of hot workingand cold working, maintained at a temperature of at least 500° C. andthen rapidly quenched, and then subjected to an aging treatment at sucha temperature distribution that decreases continuously or stepwise in adirection from a base end to a tip end of said catheter, wherein thehighest temperature in the temperature distribution is 250-350° C. andthe lowest temperature in the temperature distribution is less than 250°C.
 15. The catheter according to claim 12 wherein said reinforcing metalmember is at least one thin copper-based alloy wire extending along saidcatheter.
 16. The catheter according to claim 12 wherein saidreinforcing metal member is a braid of thin copper-based alloy wires.17. The catheter according to claim 12 wherein said reinforcing metalmember is a coil of a thin copper-based alloy wire.